Electric field at (x,y) from uniformly charged rod.

1. The problem statement, all variables and given/known data
A thin rod carries a charge Q distributed uniformly over its length L , and is situated on the x axis between x=±L/2. Find the electric field at an arbitrary point (x, y). (You will have to do separate integrals for the x and y components.)

2. Relevant equations
∫dE=∫kdq/r2

3. The attempt at a solution

Mastering Physics is telling me that the answer does not depend on k, lambda or a, which are variables I defined.

I have another method of attempting the question which results in a nasty integration, it's basically Mastering Physics being very ambiguous in what I am allowed to define. As seen here: